Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down on April 23, and its replacement, statalist.org is already up and running.

# st: boxplot whiskers with -lv- versus -adjacent-

 From "William M. Doerner" To statalist@hsphsun2.harvard.edu Subject st: boxplot whiskers with -lv- versus -adjacent- Date Tue, 11 May 2010 10:43:35 -0400

```Does anybody know what the -graph box- and -adjacent- commands are
computing for their whiskers?  They aren't using the typical +-1.5*IQR
formula as listed in the help files and used by -lv-.

adjacent values are not lower=Q1-1.5*IQR and upper=Q3+1.5*IQR.  The
command -lv- computes the adjacent values with that formula, but it
does not adjust the fence for min/max values.  I am puzzled.  I looked
at the code, but I couldn't figure it out why the commands have
different outputs.  Here is what I was running:

**BEGIN**
use http://www.stata-press.com/data/r11/bplong, clear
*graph box bp, over(when) over(sex)
keep if sex==1 & when==2
summarize bp, detail
local u=r(p75)+(3/2)*(r(p75)-r(p25))
local l=r(p25)-(3/2)*(r(p75)-r(p25))
local l=max(`l',r(min))
local u=min(`u',r(max))

di `u'
di `l'

lv bp
graph box bp, ylabel(#50, angle(horizontal))
*Notice how the upper limit should be 173 instead of 169.
**END**

The difference between the commands is not as simple as "it's 5% and
95%."  That looks true for the bp dataset, but it doesn't happen with
the city temperature dataset.  Here is more code to compare:

**BEGIN**
use http://www.stata-press.com/data/r11/bplong, clear
local x "if sex==1 & when==2 & bp~=."
summarize bp `x', detail
lv bp `x'

sysuse citytemp.dta, clear
summarize tempjuly, detail
lv tempjuly
**END**

Thanks in advance for any input!

Will Doerner

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```